基于快速M变换的多焦视觉电生理检查系统的设计

多焦视觉电生理是一种客观的、无创的视功能检查方法,可以同时检查视网膜多个微小区域的视功能,在眼底疾病的早期诊断上有独特的优势。本文介绍了多焦视觉电生理检查系统的原理与设计,它利用Windows98以上的微软操作系统特有的多显示技术,控制图形刺激器产生特殊的六边形阵列,由m序列控制六边形阵列的黑白翻转来对视网膜的各个区域分别进行刺激。然后用特制的Burian-Allen电极把由视网膜多个区域产生的混合叠加信号提取出来。信号经过放大、A/D转换后送入计算机。计算机利用快速M变换对混合信号进行分离,从而得到视网膜各个区域的反应信号。快速M变换可以将互相关计算转换为FWT,从而大大节省了计算时间。     

多焦技术及其在mERG中的应用

多焦技术是目前信号处理的一项先进技术,它在视觉电生理系统中的主要应用为多焦视网膜电图(multifocal electroretinogram,mERG)及多焦视诱发电位(multifocal visual evoked potential,mVEP)检测.其中,mERG可以同时刺激视网膜上多个小区域,在较短时间内反映各个小区域对应的ERG特性,从而精确快速敏感的测量视功能.本文主要从互相关函数、m-序列等入手介绍了多焦技术的原理,并对其在视网膜电图上的应用--多焦视网膜电图进行了描述,阐明了在多焦视网膜电图中如何对每个小区域的生理电响应信号进行分离.     

多导体视诱发脑电采集系统设计及视差深度诱发电位研究

我们根据科研实验要求利用现有的微机系统和临床脑电图仪建立了一套适用脑认知科学研究的多导视觉诱发脑电（VEP）信号采集处理系统。该系统既能满足部分临床应用的需要,同时也能根据实验要求,进行立体视觉认知过程脑电（EEG）的信息提取和分析处理。通过立体视觉深度相关脑诱发电位提取及比较分析,对深度相关的特征视觉诱发电位发放进行了标定。实验系统的建立为我们深入研究立体视觉相关脑功能和体视认知过程提供了有力的手段。     

多焦视网膜电流图中诱发成分的生理含义的解释和分离方法研究

诱发成分是指出现在mfERG一阶响应中较后的位置上的一个波形结构。本研究的第一个目的是要对诱发成分的生理含义作出准确描述，另一个目的是提出一个从一阶响应中完整，准确的分离诱发成分的方法。首先，通过分析诱发成分的各个组成信号的视网膜生理含义，指出诱发成分是一阶响应的一个固有成分，表现了视网膜的光适应机制，在波形和生理含义上与mfERG高阶响应相似但存在明显差别。其次，利用在不同刺激频率条件下得到的一阶响应之间的差异特性，设计实验从一阶响应中分离出诱发成分。实验结果还证实了本研究中关于诱发成分和高阶响应在波形上存在差异的推论。     

基于内容的图像与视频检索技术研究

本文介绍了图像和视频检索技术的目前状况及几个有特色的CBIR系统，探讨了CBIR系统的体系结构、底层视觉特征和高层语义特征的提取与表达方法，以及基于内容视频检索的镜头边界检测、视频镜头内容表示和视频高层语义表示等技术，提出了该领域存在的问题和未来发展方向。     

Effects of Vibrotactile Background on the Somatosensory Evoked Response

The somatosensory evoked response (SER) to Vibrotactile stimuli superimposed on a constant vibrotactile background of different intensities was studied in 5 subjects. It was found that vibrotactile background of low intensity enhanced the amplitude of the SER. Further increase of the intensity of the background caused a decrease in the SER amplitude. These resulted are compared to evoked response studies in visual and auditory systems.     

Correlation Between the Chromatic Visual Evoked Response and McCollough Aftereffect

Eighteen subjects received a 10-min exposure to alternating stripe-color patterns designed to elicit the orientation-specific McCollough red and green complementary aftereffect (CAE). They were also exposed to 7 Hz flickering red and green light in order to elicit the chromatic visual evoked response (CVER) from occipital and vertex electrodes. Spectral analysis of the sinusoid-like occipital CVER was then compared with strength of aftereffect. Although CVER activity at the fundamental frequency did not correlate significantly with CAE. significant correlations were obtained for CVER activity at higher harmonic frequencies. The results showed that 14 and 21 Hz activity of the green CVER correlated positively with green CAE, and 21 and 28 Hz activity of the red CVER correlated positively with red CAE. These findings agree with the hypothesis that color coding of red involves a faster neural system. Moreover, it appears that achromatic test stimuli elicit complementary aftereffects, the subjective strength of which is not related to the CVER of the training color, but rather the effectiveness of the experienced color to evoke CVER harmonic activity during direct stimulation.     

利用VEP测量视觉系统红,绿通道的反应时间差

本文应用彩色诱发电位（ＣＯＬＯＲ ＶＥＰ）在专门研制的双计算机互连系统，对人眼视觉系统中颜色通道的时间响应特性作初步研究，实验发现，在等主观亮度而颜色不同的棋盘格图形翻转刺激下ＶＥＰ中Ｎ１波的伏期因刺激颜色不同而不同。对实验结果的数据做统计的分析得出人眼颜色并行通道对三基色的响应有明显的差别，绿通道快于红通道。此结果１９９０年ＳＳ．Ｍ．Ｃｏｕｒｔｎｅｙａｎｄ Ｇ．Ｂｕｃｈｓｈａｕｍ提出的视觉颜色的     

The Effects of Attention, Stimulus Intensity, and Individual Differences on the Average Evoked Response

The effects of shifting attention toward or away from visual or auditory stimuli of varying intensities were studied using average evoked responses (AERs) in 24 normal human volunteers. Ss were asked to attend to visual or auditory stimuli of four intensities (randomly presented) or to ignore the lights and tones and do mental arithmetic. For visual stimuli, attentional effects were largest at low intensities whereas for auditory stimuli equal effects were shown across intensities. Similar individual rates of increase of AER amplitude with increasing intensity were observed for both visual and auditory stimuli when attentional conditions were controlled. These results suggest that some general intensity processing response is reflected in the AER and that it is important to control attention in AER experiments.     

The Effect of Unilateral Alpha Training on Visual Evoked Response in a Dyslexic Adolescent

To further elucidate the possible relationship between alpha waves and the averaged visual evoked response (VER), a pilot study with a dyslexic adolescent was undertaken. Baseline alpha and VER were recorded and bilateral alpha training done. After each trial the VER was recorded. By analysis of variance it was found that alpha training significantly increased the amplitude of VER (p < .001). Baseline values for amplitudes of the VER fluctuated widely from zero but were not correlated with percent alpha. Next a system was devised to train alpha unilaterally. The subject was given a feedback response when he produced 0.5 sec of alpha in the left hemisphere and concurrently 0.5 sec of beta or theta in the right hemisphere. Alpha time on the left significantly increased over the 5 day (4 trials per day) period, as did beta and theta time on the right. Left minus right VER amplitude difference was also increased and correlated (p < .05) with both alpha (L) and beta or theta (R) percent time increases.     

基于眼电和稳态视觉诱发电位分析的目光跟踪方法

眼动跟踪技术作为人机交互手段和行为检测方法已广泛应用于心理学和认知科学领域的研究,基于稳态视觉诱发电位的脑-机接口也是一种备受关注的人机交互方法。本研究提出一种结合眼电和稳态视觉诱发电位同步分析的眼睛注视点位置跟踪方法,通过同步检测两种电生理信号:眼电信号(EOG)和脑电信号(EEG)来实现。主要的处理算法有:基于EOG的人机交互算法,包括基线去除、去噪声、角度变换、基准校正等;基于SSVEP的脑-机接口算法,通过典型相关分析法实现。由SSVEP判断出的目标对应的屏幕坐标可以作为眼动分析中基准校正的输入参数。实验结果表明:每0.5 sEOG-HCI可以对注视点位置进行一次识别;每2 sSSVEP-BCI可以对注视目标做一次判别;两者既可以独立运行,也可以协同工作,相比单一信号的人机交互方法,可以缩短判断时间和提高准确率。     

最大长度序列诱发听性脑干反应的线性与非线性成分引出率和稳定性分析

在记录常规的听性脑干反应(cABR)时,听觉系统被视为一个线性系统,无法获取反映听觉系统非线性特性的成分。而采用最大长度序列(MLS)刺激,对记录的反应建立Volterra级数展开模型,能够同时获取反映听觉系统线性与非线性特性的不同成分,所获取的ABR被称为MLS-ABR。由于这种方法在实验和计算方面的困难,现阶段对MLS-ABR的特性了解尚少,所以通过实验研究对其引出率及稳定性进行分析。利用MLS方法提取非线性成分,选择一个9阶MLS,提取11例正常青年人的MLS-ABR及cABR,其中MLS-ABR的一阶和一个二阶核切片（VS1和VS21）的波形清晰完整,分别表达ABR的线性和非线性成分。以cABR、VS1、VS21中各特征波出现率、潜伏期及峰峰值变异系数为考察指标,对照分析cABR与MLS ABR的线性、非线性成分引出率和稳定性。结果发现,MLS-ABR中线性成分各特征波引出率都较高（>90%）,且其潜伏期（1、3、5潜伏期波变异系数分别为5.17、3.70、2.00）比cABR（Ⅰ、Ⅲ、Ⅴ波潜伏期变异系数分别为6.54、3.70、2.87）更加稳定;非线性成分也可稳定引出1、3、5波（>80%）,并且非线性成分的在5波的表达更加强烈。进一步证实MLS在获取ABR非线性成分的可靠性,加深对MLR-ABR的认识,为后续相关研究提供重要依据。     

The Single Training Sample Extraction of Visual Evoked Potentials Based on Wavelet Transform

Based on the good localization characteristic of the wavelet transform both in time and frequency domain, a de-noising method based on wavelet transform is presented, which can make the extraction of visual evoked potentials in single training sample from the EEG background noise in favor of studying the changes between the single sample response happen. The information is probably related with the different function, appearance and pathologies of the brain. At the same time this method can also be used to remove those signal＇ s artifacts that do not appear with EP within the same scope of time or frequency. The traditional Fourier filter can hardly attain the similar result. This method is different from other wavelet de-noising methods in which different criteria are employed in choosing wavelet coefficient. It has a biggest virtue of noting the differences among the single training sample and making use of the characteristics of high time frequency resolution to reduce the effect of interference factors to a maximum extent within the time scope that EP appear. The experiment result proves that this method is not restricted by the signal-tonoise ratio of evoked potential and electroencephalograph （EEG） and even can recognize instantaneous event under the condition of lower signal-to-noise ratio, as well as recognize the samples which evoked evident response more easily. Therefore, more evident average evoked response could be achieved by de-nosing the signals obtained through averaging out the samples that can evoke evident responses than de-nosing the average of original signals. In addition, averaging methodology can dramatically reduce the number of record samples needed, thus avoiding the effect of behavior change during the recording process. This methodology pays attention to the differences among single training sample and also accomplishes the extraction of visual evoked potentials from single trainings sample. As a result, system speed and accuracy could be improved to a great extent if this methodology is applied to brain-computer interface system based on evoked responses.     

基于叠加原理的合成稳态视觉诱发电位

检验高刺激率诱发的稳态视觉诱发电位(SSVEP),可以被看作是低刺激率诱发的瞬态视觉诱发电位(tVEP)的线性叠加的科学假设。采用模式翻转视觉刺激,记录10名健康成年人在不同刺激率(4, 7.1, 7.7, 8.3, 9.1,10, 11.1, 12.5, 14.3, 16.7, 20, 25 rev/s)条件下的视觉诱发电位(VEP),然后用低刺激率(4 rev/s)诱发的tVEP及其经过幅值和相位调整后的波形,分别与刺激序列卷积合成对应高刺激率下的SSVEP,并采用Hotelling T²检验比较各tVEP模板条件下合成SSVEP与实际记录SSVEP波形之间的异同。结果显示,当使用常规记录的tVEP作为模板时,基于线性叠加原理合成的与实际记录的SSVEP在7.1~9.1 rev/s刺激率范围内不存在显著性差异(P>0.05),而在10~25 rev/s刺激率范围内存在统计学差异(P< 0.05),且两者之间误差随刺激率增加而增大;当对tVEP模板进行幅值和相位调整后,合成与实测SSVEP之间无统计学差异(P> 0.05),两者间的误差也显著下降,在被测刺激率范围内基本保持平稳。结果表明,不同刺激率下的瞬态诱发反应存在差异,稳态与瞬态诱发电位之间的线性叠加假设有赖于对各个刺激率下瞬态诱发电位的测定。